Population genetic theory will be developed to predict levels of variation and degrees of association for genetic markers in a variety of models of population structure, mating system and mutation regime. Particular attention will be paid to restriction fragment length polymorphisms and to DNA sequences. Statistical methodologies for making inferences from these kinds of data will be developed. Work will proceed in four principal directions. The first will be concerned with linkage disequilibrium for restriction sites. Expected values for squared disequilibria will be found for segregating sites and a numerical study made of the temporal behavior of these quantities. Testing hypotheses about disequilibria will take account of lower-order disequilibria and departures from random mating. The second area will be concerned with the statistical properties of populaton genetic parameter estimates, with emphasis on resampling methods. Jackknifing and bootstrapping will be compared for quantities such as average heterozgosity. Diagnostic procedure will be explored to identify features of data that can lead to negative variance components in hierarchical analyses of gene frequencies. As a third topic, a suite of trigenic and quadrigenic identity coefficients will be evaluated for loci undergoing gene conversion. Such quantities will allow variance for digneic measures of identity or disequilibrium to be predicted. Both inter- and intra- chromosomal gene conversion will be incorporated into this theory, as well as drift, mutation and recombination. The fourth major area will be concerned with measures of distance between DNA sequences. The availability of several sequences for a population or species requires that the effects of drift be included in theories for the variance of distance measures. The amalgamation of within- and between-population variance is made complicated by lack of knowledge of properties of founding populations, and the necessity to allow mutation to be among four bases.